10 most difficult genetics riddles

DNA was first isolated by the Swiss physician Friedrich Miescher who, in 1869, discovered a microscopic substance in the pus of discarded surgical bandages. As it resided in the nuclei of cells, he called it "nuclein". In 1878, Albrecht Kossel isolated the non-protein component of "nuclein", nucleic acid, and later isolated its five primary nucleobases.

Progeria is an extremely rare genetic disorder in which symptoms resembling aspects of aging are manifested at a very early age. Those born with progeria typically live to their mid-teens to early twenties. It is a genetic condition that occurs as a new mutation, and is rarely inherited as carriers usually do not live to reproduce.

Interbreeding between Neanderthals with modern humans took place several times. Neanderthal-derived DNA was found in the genome of contemporary populations in Europe and Asia, it accounts for 1–4% of modern genomes. Neanderthal genes are absent from most modern populations in sub-Saharan Africa.

This kind of coat coloring, which combines two colors other than white (black and red in this case), is known as tortoiseshell, and it is found almost exclusively in female cats. This is because the X chromosome determines the color of the cat, and there are no color genes in Y chromosome. Thus, female cats with XX chromosomes may be three colored (including white), while male cats with XY chromosomes cannot. (with the exception of very rare XXY sterile males).

The U.S. Supreme Court in 2013 held that human DNA was a "product of nature", a basic tool of scientific and technological work, thereby placing it beyond the domain of patent protection. It struck down patents held by Myriad Genetics Inc, a Utah company, on two genes linked to a higher risk of breast and ovarian cancer. The ruling represents a major shift in the law, overturning three decades of patent awards by the US government and could have a profound effect on the biotechnology and drug industry.

The first genetically modified animal to be commercialized was the GloFish, a Zebra fish with a fluorescent gene added that allows it to glow in the dark under ultraviolet light. It was released to the US market in 2003. GloFish available in pet stores are now sold in bright red, green, orange-yellow, blue, pink, and purple fluorescent colors. In the European Union, the placing on the market and breeding of genetically modified animals is prohibited.

In genetics, a centimorgan (abbreviated cM) is a unit for measuring genetic linkage. It is defined as the distance between chromosome positions for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01. It is often used to infer distance along a chromosome. However, It is not a true physical distance.

The cultivated kiwi fruit, Actinidia deliciosa, is a hexaploid species with a total number of 174 chromosomes. Many of cultivated plants are polyploids created by selective breeding, and are usually unable to interbreed with their diploid ancestors.

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

The Manx taillessness gene is dominant; kittens from two Manx parents are generally born without any tail. However, having two copies of the gene is lethal in utero, so breeders avoid breeding two entirely tailless Manx cats together. Typically, when bred with non-Manx cat, tail length is random throughout a litter of kittens.